1. Field of the Invention
This invention relates to improvements in ramps for elevating vehicles to positions above the surface of the ground, and more particularly, but not by way of limitation, to a ramp having more than one angular ramp portion whereby the vehicle may be driven along the ramp at a total angle greater than that permitted by the structural characteristics of the vehicle.
2. Description of the Prior Art
It is common practice today to mount relatively small or portable drilling rigs on vehicles whereby the drilling rig may be transported to the site of a well bore and erected for a well drilling operation, or the like. Subsequent to the well drilling operation, these drilling rigs may be removed from the well site, and transported to another location by the vehicle in order that the drilling rig may be used for drilling additional well bores. The vehicles normally comprise large off-highway type structures of a relatively long overall length for carrying the drilling rig in a horizontal position during transporting thereof from site to site. It is the usual practice to provide two sets of running wheels for these vehicles, with one set of wheels being disposed in the proximity of the rear of the vehicle. At the well bore site, the vehicle is positioned in such a manner that the drilling rig may be hoisted to a vertical or upright position, with the location of the rig being at an optimum for normal use during the well drilling operation. Of course, most of the weight of the erect drilling rig is supported by the forward or leading wheels of the vehicle. In addition, the remaining portions of the vehicle bed support the draw works and other equipment necessary for the well drilling operation, as is well known.
In the light of current concern about the ecology, and environment, and the like, it has become necessary to utilize a considerable amount of additional equipment at the surface of a well bore, such as blow out preventers, and the like. As a result it is necessary to position the drilling rig in such a manner that the elevation thereof, and particularly the elevation of the drilling platform provided thereon, be sufficient for providing clearance for these blow out preventers, and the like. Since the overall length and general construction of the vehicle upon which the drilling rig is mounted permits the vehicle to travel along a ramp having an angle no greater than seven degrees from the horizontal, the problem of positioning the drilling rig at greater elevations is difficult. In some instances, the usual hydraulically actuated stilts or jacks utilized for stabilization of the rigs have been installed or supported at the bottom by channel beams, base structers, or the like, but these have not been entirely satisfactory in that the weights and normal working conditions during the drilling of a well bore are often too great for this type supporting arrangement.